Products which are tri-proof (waterproof, dustproof, and shockproof) are desirable. A conventional tri-proof structure usually include a first casing, a waterproof rubber ring, and a second casing. The first casing is provided with a first soft rubber. The first soft rubber and the first casing are double-color molded. The second casing is provided with a second soft rubber. The second soft rubber and the second casing are also double-color molded. The first soft rubber and the second soft rubber cooperatively form a soft rubber surface, the soft rubber surface provides a buffer and shockproof effect. Simultaneously, the second casing further defines a groove, the waterproof rubber ring is assembled in the groove. The first casing presses on the waterproof rubber ring and is assembled together with the second casing via a fixing member. In the aforementioned structure, the first soft rubber and the first casing are double-color molded, and the second soft rubber and the second casing are double-color molded. A structure of the mold is complex, a cost of the mold manufacture is high, and a precision requirement to the molding machine is high, thus the manufacturing cost of a mobile phone is increased. In addition, because of the sole complete circle structure and a small cross-section area of the waterproof structure, during the process of assembling the waterproof structure to the groove, the operation is inconvenient, and the assembly has an inferior consistency and a structural bias. Thus the waterproof effect is affected. In an aspect of the waterproof and sealing effect, the waterproof effect of the structure mainly depends on a degree of pressure and sealing between the waterproof rubber ring and the first casing and between the waterproof rubber ring and the second casing. Moreover, the waterproof rubber ring has manufacturing tolerances and assembly biases, thus a larger interference value is required to ensure the waterproof effect. A greater locking force is accordingly required between the first casing and the second casing and a larger casing strength is accordingly required. In addition, there exists an assembly line after the assembly of the first casing soft rubber and the second casing soft rubber, which can affect the aesthetic appearance of the product. Simultaneously, the first casing soft rubber and the second casing soft rubber only provide a buffer and shockproof effect, and the waterproof rubber ring only provides a waterproof and dustproof effect, all must be used simultaneously to achieve a tri-proof effect.